Cartridge fuses with non-porous arc-quenching material



y 2, 1967' L. J. SAUDICOEUR 3,317,689

CARTRIDGE. FUSES WITH NON-POROUS ARG-QUENCHING MATERIAL Filed March 30,1964 INVENTOR BY w w ATTORNEXB United States Patent France, France,

The present invention relates to cartridge fuses of the kind comprisingfusible Wires or strips embedded within a mass of arc quenching materialbetween two end caps which carry appropriate contact devices, such asblades or tags.

In the conventional construction the arc quenching material is underpulverulent form and it is enclosed, together with the fusible element,within a tubular bodyor barrel the ends of which are closed by the endcaps. The filing of these cartridge fuses is tedious and delicate.Further the fusible elements are not rigidly maintained by thepulverulent material against the action of shocks, vibrations andaccelerations (such as centrifugal force) which may cause their rupture,more particularly when they are brought to a relatively high temperatureby passage of their rated electric current.

It has already been proposed to embed the fusible elements in a mouldedmass of synthetic resin together with the end caps. But this arrangementhas the disadvantage that when the fusible elements are submitted for along time to a current of relatively high intensity, they are brought toa suflicient temperature for slowly decomposing the synthetic resin,thus producing carbon deposits which are more or less electricallyconducting and tend to facilitate the production of the arc in the caseof a heavy short-circuit.

In accordance with the present invention the fusible elements areembedded in a moulded mass of compact solid mineral silicate. Such amass is substantially unaffected by the temperatures which the fusibleelements may reach in normal operation and even if some kind of reactiontakes place it only leads to the formation of a highly insulating glass.

If desired, the mineral silicate may contain pulverulent silica as afilter. The moulded mass of mineral silicate is preferably enclosed inan outer tubular body or barrel. It is besides possible to providewithin the moulded mass a cavity filled with any known are quenchingfluid such as sulphur hexafiuoride.

The cartridge fuse according to the invention may be manufactured byfirst disposing the fusible elements and the end caps in the outertubular body or barrel, by injecting thereinto a plastic mass of aqueoussodium silicate and in thereafter heating the cartridge at about 150 C.for eliminating the excess of water. The mass then sets in the form of acompact hard solid body.

Pure pulverulent silica may conveniently be added as a filler to theaqueous silicate before proceeding to the injection step. In amodification the pulverulent silica may be introduced into the outerbarrel before the injection step.

It is also possible to realize the injection step in a separate mouldand thereafter to dispose the solid mass in the outer tubular body orbarrel, together with the fusible elements and the end caps.

In the annexed drawings:

FIG. 1 is a longitudinal section of a cartridge fuse according to thisinvention, comprising an outer barrel.

FIG. 2 is a longitudinal section of a modified embodiment having aninner cavity filled with an arc quenching fluid.

Referring to FIG. 1, the contacting blades 1 are formed integral withcylindrical end caps 2 which are fixed by radical screws such as 3 atboth ends of an outer tubular body or barrel 4 made of an appropriateinsulating material. The end caps 2 comprise inner central bosses 5 onwhich are soldered the ends of fusible elements 6, such as silverstrips. The outer barrel 4 has a lateral hole 4a through which a plasticmass of mineral silicate has been injected into the said outer barrel.This mixture has set in the form of a compact solid body 7 in which thefusible elements are wholly embedded and are thus fully protectedagainst shocks, vibrations or accelerations. Further the silicate mass 7is unaffected by the temperatures to which the fusible elements may bebrought in normal operation, and in any case it could only betransformed into a highly insulating anhydrous glass-like substancewithout producing any carbon deposit between the end caps 2.

The injection hole 401 is of course sealed by the silicate mixtureitself. It is besides obvious that this hole could also be provided inone of the end caps 2. The crosssection of the outer barrel may becircular, square, rectangular, polygonal, or of any other shape, asdesired.

The plastic silicate mass is preferably formed of aqueous sodiumsilicate comprising for instance 60 to water, the cartridge being heatedto about C. after the injection step for eliminating the excess ofwater. Pure pulverulent silica may be added to the plastic mass as afilter.

Alternatively the plastic mass could be injected into a separate mould,the solid body thus obtained being there after disposed in the outerbarrel together with the fusible elements and the end caps.

The cartridge fuse of FIG. 2 is substantially similar to the embodimentof FIG. 1, but it comprises an inner cavity 8 with a canal which openslaterally through the outer barrel 4, the fusible elements 6 beingexposed in the said cavity. This cavity 8 has been filled with an arcquenching fluid, such as sulphur hexafluoride SP and it has been sealedby means of a plug 9. When the fusible elements melt, the arc isimmediately quenched by SF in the per se known manner.

The cavity 8 may be realized by means of a small wax core moulded on thefusible elements 6 and disposed in the outer barrel together with theseelements. When the silicate mass has been injected and has set, thiscore is easily eliminated by fusion.

In a modification the sulphur hexafluoride could be contained in a smallglass bulb disposed in the central zone of the cartridge and which wouldbreak or burst under the action of heat when the fusible elements melt.

While in FIGS. 1 and 2 the end caps 2 have been shown as engaged intothe ends of the outer barrel 4, they could also be secured against theend faces of the latter, in the per se known manner.

I claim:

1. A cartridge fuse comprising an open-ended insulating outer tubularbarrel having a lateral hole; two electrically conducting end caps, eachsecured to one end of said barrel so as to define an intermediate innerspace therein; electrically conducting fusible elements connecting saidend caps with each other within said inner space; and a compact, solidand non-porous mass of a watersoluble mineral silicate embedding saidfusible elements and substantially filling said inner space and lateralhole to prevent relative shocks and vibrations of the cartridge fuseassembly.

2. A cartridge fuse comprising an open-ended insulating outer tubularbarrel; two electrically conducting end caps, each secured to one end ofsaid barrel so as to define an intermediate inner space therein;electrically conducting fusible elements connecting said end caps witheach Patented May 2, 1967- other within said inner space; and a compact,solid and non-porous mass of a Water-soluble mineral silicate embeddingsaid fusible elements and substantially filling said inner space, saidmass having formed therein a substantially central cavity in which saidfusible elements are exposed, and said cavity being filled with anarc-quenching fluid.

3. In a cartridge fuse as set forth in claim 2, the tubular barrel andthe non-porous mass having registering holes therein through which thearc-quenching fluid is introduced, and a plug insert sealing saidregistering holes to retain said fluid in said inner space.

References Cited by the Examiner UNITED STATES PATENTS 1,266,479 5/1918Jensen 200-135 1,270,335 6/1918 Schweitzer 200-135 1,480,225 1/ 1924Snook ZOO-120 4 Murray 200-120 Schweitzer 200120 Hill 200-120 Lohausen200-120 Strom 200-117 Yonkers 29-1555 Miller 200-120 Fister 200-120Skeats 200-120 Arzapalo 200-120 Hollman et al. 200-120 Hollrnan et al.200-120 Great Britain.

BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON, Assistant Examiner.

1. A CARTRIDGE FUSE COMPRISING AN OPEN-ENDED INSULATING OUTER TUBULARBARREL HAVING A LATERAL HOLE; TWO ELECTRICALLY CONDUCTING END CAPS, EACHSECURED TO ONE END OF